1. Field of the Invention
This invention pertains to the field of photonic bandgap technology. More particularly, the invention pertains to a waveguide that permits the virtually lossless unidirectional propagation and phase shift of light.
2. Discussion of the Background
Over the past couple of decades, active and passive devices ranging from optical switches to complex integrated networks have been developed in the data communication and optics industries
Recently, the data communications and optics industries have experienced high demand for various types of small-scale opto-electronic devices. The importance of optical waveguides for both single and multi-mode transmission is unquestionable—particularly in the 1.3-1.6 μm region of commercial S-, C- and L-bands.
Along with index-step guiding, or guiding through total internal reflection, certain classes of waveguides can guide light by Bragg reflection, or by photonic band gaps (PBGs).
Waveguides can be utilized as phase modulators by applying an electric field to the waveguide. Phase modulation occurs by means of an electro-optic effect as the electric field reacts to the waveguide. Metal electrodes or plates are placed on opposite sides of the waveguide and with the application of an electrical field, phase modulation occurs in the propagating light beam. As a rule of thumb, the larger the applied electric field, the shorter one can design the waveguide.
However, in prior art devices, as the distance between the metal plates decreases, absorption or loss of the light energy substantially increases. This absorption problem of the prior art is illustrated in FIG. 1. As light 16 is propagated and reflected in guide region 12 of waveguide 10, losses 18A, 18B, 18C are absorbed in the cladding 14A, 14B.
In that spatial economy is a desired feature in electro-optic systems, a need is seen for a device that allows for a small separation of distance between the metal electrodes while minimizing optical loss in the waveguide.